5. Блок 1: 1/2 + 31/20. Блок 2: 4/5 : 2/7. Блок 3: (1/5 + 8/15) · 6.

Блок 1: \(\frac12+\frac{31}{20}=\frac{10}{20}+\frac{31}{20}=\frac{41}{20}\).

Блок 2: \(\frac45:\frac27=\frac45\cdot\frac72=\frac{14}{5}\).

Блок 3: \(\left(\frac15+\frac8{15}\right)\cdot6=\frac{11}{15}\cdot6=\frac{22}{5}\).

Ответ: \(\frac{41}{20};\ \frac{14}{5};\ \frac{22}{5}\).